FIG. 1 is a block diagram illustrating selected elements of conventional network 100. Conventional network 100 includes one or more Internet Protocol (IP) routers (e.g., IP router 110) surrounding a domain 120 of circuit providing elements (e.g., switch 130). The IP routers and circuit providing elements are connected together by a number of links (e.g., link 140 and 150). A link is a physical or logical connection between two points capable of transporting digitally encoded voice and data traffic.
The circuit providing elements within domain 120 may be Asynchronous Transfer Mode (ATM) switches, Time Domain Multiplexing (TDM) switches, Wavelength Division Multiplexing (WDM) optical cross-connects (OXCs), or the like. The term “switch” may refer to an ATM switch, a WDM cross-connect, a TDM switch or similar circuit providing element. Typically, domain 120 comprises an optical layer of conventional network 100 and the one or more IP routers (e.g., IP router 110) comprise an electrical layer of conventional network 100. The optical layer's primary function may be to provide circuit services to the one or more IP routers. Circuit services refer to services provided to nodes to establish temporary connections between the nodes.
FIG. 2 is a block diagram illustrating the logical decomposition of IP router 210 and TDM switch 220. IP router 210 and TDM switch 220 may be logically decomposed into a control plane, a management plane, and a forwarding plane. The logical decomposition of IP router 210 and TDM switch 220 into these three planes provides a means for network engineers to more easily design networks comprising nodes of different switching technologies.
The term control plane refers to the entities involved in the functions of signaling and routing within a network. Signaling is the process of exchanging control messages between network nodes and is typically used for dynamic connection set-up across a network. Routing refers to adjacency discovery, propagation of reachability information, path calculation, path selection process and the like. Control plane entities may include control plane processors 241 and 243, various software processes, and the like.
The term management plane refers to the entities involved in the functions of configuring and managing a node (e.g., IP router 210 and TDM switch 220). The management functions may relate to management of devices, of the networking layer, of services, or the like. Management plane entities may include management processors 251 and 253. A person of ordinary skill in the art will recognize that a single processor may be used to perform both control plane functions and management plane functions.
The term forwarding plane refers to the entities involved in the manipulation and forwarding of digitally encoded voice and data. Examples of forwarding plane entities include line cards (e.g., line cards 255 and 257), Forwarding Information Bases (not shown), and the like.
Referring again to FIG. 1, the IP routers and the circuit providing elements form two distinct domains (e.g., an IP domain and a transport domain). The routing, topology distribution, and signaling protocols in the IP domain are independent of the routing, topology distribution, and signaling protocols in the transport domain. Since the IP domain and the transport domain run separate instances of routing and signaling protocol processes, the control plane of the IP domain is independent of the control plane of the transport domain.
In the past few years, there has been significant interest within the industry to move towards a unified set of mechanisms that will enable service providers to manage separate network elements in a uniform way. Such a unified set of mechanisms is central to managing a network composed of a wide range of elements, from IP routers, to Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) cross connects, to optical cross-connects. The traditional transport network, for example, has so far not had such a common framework. Indeed, the SONET network infrastructure does not have any control plane at all (it has only a management infrastructure) because the need for automatic provisioning was not envisioned when SONET/SDH networks were initially developed. As the extent of SONET networks grew, however, the manual provisioning process became increasingly slow and often error prone, motivating the need for a better solution. In parallel, the Internet Protocol (IP) and its associated protocols have matured to become the ubiquitous routing and signaling mechanisms for transporting packet data. Further, this packet infrastructure also has evolved to introduce the idea of decoupling routing from packet forwarding (via multi-protocol label switching, for example), thus allowing for virtual circuit setup and traffic engineering in packet networks.